It's not really acceptable, but online dating is a weird environment where the normal rules don't apply. For example, women receive plenty of unacceptable behaviour online from men sending dick pics, so this cuts both ways.

Just don't be one of the bad guys and ignore the insecure women who believe height is a deal breaker, they are doing you a favour by removing themselves out of your potential pool of dating partners.

I'm pretty short at 5'4" and online dating never worked for me. I met my wife in the real world and we've been happily married for 10 years now. And she's 5'9", so there are plenty of decent women out there who don't give a shit about height.